1. Field of the Invention
The invention relates in general to gas-insulated transmission lines and in particular to a non-binding inner conductor load bearing roller for a gas insulated transmission line having a corrugated outer conductor.
2. Description of the Prior Art
Motion occurs between the inner conductor/insulating means assembly and the outer conductor of a gas insulated transmission line both when the transmission line is first assembled at the factory and while it is in service due to temperature differences between the outer and the inner conductors. The temperature changes may be due to changes in the continuous current and in the ambient temperature the gas-insulated transmission line is operating in.
Previous gas-insulated transmission lines utilized a skid contact member located at the end of the insulator and motion occurred between the skid and the tubular outer sheath. The motion between the skid and the outer sheath may produce particles which reduce the voltage withstand ability of the gas-insulated transmission line. In order to eliminate the production of particles, a roller assembly was installed in place of the skids.
A recent development for gas-insulated transmission lines uses corrugated aluminum for the outer conductor or sheath instead of the smooth elongated aluminum type used previously. The roller or skid design of previous gas-insulated transmission lines, when applied to a corrugated outer conductor or sheath, will have the disadvantages that the inner conductor/insulating means assembly will be forced to rise and fall with the corrugations and the force to obtain this axial motion upon assembly or during service will be high.
A good reliable transport means for the inner conductor/insulating means/particle trap assembly which retains the advantages of minimum production of particles and the low axial force of the previous roller design, and transports the inner conductor/insulating means/particle trap assembly axially within a corrugated sheath outer conductor without radial displacement is disclosed in concurrently filed copending U.S. patent application Ser. No. 439,247, entitled "Conductor Load Bearing Roller For A Gas-Insulated Transmission Line Having A Corrugated Outer Conductor", by W. H. Fischer and K. H. Yoon and assigned to the same assignee as the present invention. While the transport means disclosed in this patent application provides for axial movement without radial displacement, it is possible that the transport means may bind upon insertion of the insulator/particle trap/inner conductor assembly into a corrugated outer conductor having steep slopes to the corrugations. The present application discloses a transport means providing the same excellent transport of the insulator/particle trap/inner conductor assembly axially along a corrugated outer sheath without radial displacement and having the additional desirable feature of not binding for any slope of the corrugations less than vertical.